This is a plugin for the Sublime Text text editor (both versions 2 and 3) that provides a number of useful commands for GitHub, including creating and browsing gists, opening and editing files on GitHub, and bringing up the blame and commit history views. You can install via Sublime Package Control plugin. Just open "Package Control: Install Package" in your Command Palette and search for "sublime-github". The plugin should be picked up automatically. If not, restart Sublime Text.